Shrubs or trees with bicollateral vascular tissue and intraxylary phloem. Leaves opposite, rarely subalternate, simple, entire or at most crenulate, pellucid-punctate, these aromatic glands usually present also in other parts of the plant; stipules usually wanting. Inflorescence racemose or cymose, often paniculate, axillary or subterminal in the axils of the upper leaves before the development of the terminal bud or rarely truly terminal. Flowers 4- or 5-merous, hermaphrodite, regular, sub- tended by two opposite bracteoles. Sepals either free and usually imbricate in the bud or concrescent, calyptriform and circumscissile from the base at anthesis. Petals 4 or 5, rarely minute or wanting. Stamens usually numerous, inserted on the margin of the receptacle in 1 to several series; filaments incurved in the bud, rarely straight, often conspicuous by their length and color or at least by their number; anthers dorsifixed, rarely basifixed, 2-celled as a rule, dehiscing longi- tudinally, the connective usually terminating in a gland, the pollen trigonous, 3-porous. Ovary inferior, rarely subinferior, 2- to several-celled, the receptacle often produced above; placenta mostly axile; ovules 2 to several in each cell; style simple, filiform, the stigma small. Fruit a berry or a drupe or, in some Asiatic and Australian genera often cultivated in other countries, a loculicidal capsule; seeds without endosperm, the embryo straight or incurved with free or connate cotyledons (in the first case the radicle also free and the cotyledons either folia- ceous and contort-plicate or thick and plano-convex).

Habit

Shrubs trees

Distribution

Species about 3000, chiefly in the tropics and in Australia. In Europe only Myrtus communis. The Central American genera fall into three subtribes.

Key

A. Cotyledons free, foliaceous, more or less contort-plicate; radicle elongate, about as long as the cotyledons. Flowers mostly 5-merous, paniculate; ovary 2- to 3-celled, the ovules 2 in each cell. Berry mostly 1- or 2- seeded. (Subtribe MYRCIINAE) la. Calyx concrescent, at anthesis circumscissile and falling away like a lid, remaining attached at one point, at last quite deciduous. Indu- mentum often formed by dibrachiate hairs ........................................... 1. CALYPTRANTHES b. Sepals free, imbricate in the bud. Hairs simple . . . 2 2a. Receptacle cup-like, produced above the ovary; berry globose ............. 2. AULOMYRCIA b. Receptacle not produced above the ovary; berry usually ellipsoid or oblong .......................................................... 3. MYRCIA B. Embryo straight, either homogeneous (the cotyledons and radicle con- nate) or with free plano-convex cotyledons and short radicle. Flowers mostly 4-merous, in more or less abbreviated racemes, often glomerate, rarely solitary or cymose; ovary 2(-3)-celled, the ovules 2 to several in each cell. Berry mostly 1-seeded, sometimes several-seeded. (Sub- tribe EUGENIINAE) la. Inflorescence cymose; flowers large, the expanded cluster of stamens 2 cm. or more in diameter ....................................................... 4. SYZYGIUM b. Inflorescences glomerate or racemose, rarely solitary or cymose; flowers small, the expanded cluster of stamens less than 1 cm. in diameter ............ .2 2a. Receptacle produced above the ovary, circumscissile at base. Ovules 2 or 4, ascending, in each cell of the ovary. Flowers glomerate ........... 5. MYRCIARIA (165) This content downloaded by the authorized user from 192.168.82.203 on Tue, 27 Nov 2012 17:43:40 PMAll use subject to JSTOR Terms and Conditions[Vol. 45 166 ANNALS OF THE MISSOURI BOTANICAL GARDEN b. Receptacle not produced above the ovary. Ovules usually more than 2 in each cell of the ovary. Flowers in racemes, fascicles or glomer- ules, rarely solitary or cymose ......................................................... 6. EUGENIA C. Embryo incurved, the radicle elongate, much longer than the minute cotyledons. Inflorescence usually 1- to 7-flowered and cymose on a long peduncle (or pedicel if flowers solitary). Ovary 2- to 7-celled; ovules several to numerous in each cell. Seeds mostly numerous, small. (Subtribe MYRTINAE) Ia. Bud closed, sepals not reflexed or spreading until anthesis ..................... 9. PSIDIUM b. Bud open, sepals reflexed or spreading before anthesis ................................................................... 2 2a. Filaments incurved in the bud, filiform; anthers dorsifixed. Leaves mediocre ...........7 ....................................................................... 7. CALYCOLPUS b. Filaments straight or nearly so in the bud, flattened; anthers basifixed. Leaves very small ....................................................................................... 8. UGNI

Note

In a recent publication by E. Kausel (in Ark. Bot. n. s. 3:491-516. 1956) the following information of systematic importance concerning the germination of the seed is given: Myrcioideae (in Panama-Myrcia, Aulomyrcia and Calyptranthes): Germina- tion epigaeous, the large foliaceous, contort-plicate, ensheathing cotyledons become the first assimilating leaves of the young seedling. Myrtoideae (in Panama-Ugni, Calycolpus and Psidiurn): Germination epi- gaeous, the cotyledons very small. Eugenioideae (in Panama-Eugenia and Myrciaria): Germination hypogaeous, the cotyledons remaining in the seed under the ground. Beside the genera enumerated in the key, representatives of the Australian genera Melaleuca and Eucalyptus are cultivated in Panama. Melaleuca lencoden- dron L. is an ornamental shrub or small tree with narrowly lanceolate, alternate leaves with conspicuous longitudinal nerves and flowers in terminal spikes. It is cultivated in the Plant Introduction Garden at Summit, Canal Zone, and probably elsewhere. The most frequently cultivated species of Eucalyptus is E. globulus Labill. planted as a shade tree. Pimenta oflicinalis, the Allspice, is planted in various parts of temperate and hot regions of tropical America, but has not yet been reported from Panama.